Recent years have seen a significant and continuing increase in the demands placed on wireless communication networks, in terms of the amount of data communicated, geographic coverage, and the number of users served. Advanced communication technologies, such as 3GPP's Long-Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMax) have been developed in an attempt to address this increasing need. One solution that has been proposed for increasing coverage and throughput in future networks is the inclusion of relays capable of increasing the geographic coverage of radio access nodes. Because these relays interact with both wireless terminals and base stations, operation and management of these relays can be complicated, and efficient use of their capabilities can have a significant effect on overall system effectiveness.
The performance of a relay may be heavily dependent on the allocation of subframes between its “access link” (between the relay and a wireless terminal served by the relay) and a “backhaul link (between the relay and its donor base station). For example, if the backhaul link has poor radio quality relative to the access link, the backhaul link may become a bottleneck. In such situations, it may be beneficial to have more subframes configured for use on the backhaul link and less on the access link. On the other hand, if the backhaul link has good radio quality relative to the access link, then the access link may become a bottleneck. In such situations, it may be beneficial to have more subframes configured for use on the access link and less on the backhaul link.
Many in-hand relays use multicast-broadcast single frequency network (MBSFN) subframes for downlink transmission on their access link. Because the donor base station, or another controlling node (e.g., an Operations, Administration, and Maintenance (OAM) system), determines the MBSFN configuration for each of the relaying nodes served by the controlling node, the controlling node essentially determines the allocation between access link and the backhaul link for the managed relay. While the initial configuration can be re-configured by the controlling node, reconfiguring this allocation can take a significant amount of time, which may lead to inefficient resource utilization. For example, a change in allocation may require the donor base station to broadcast updated system information so that all wireless terminals are aware of the change in the configuration. As a result, it may be several seconds before such a change can be implemented in served wireless terminals. During this time, it may not be possible for the affected relay to use the new configuration or even, in some cases, all slots of the old configuration. This delay can make it difficult to assign more uplink slots to the access link when needed, e.g., when there is a wireless terminal with a bad connection to the relay.
Additionally, it might be beneficial for or required that the uplink and downlink configurations for the backhaul link match each other so that there is an uplink subframe a fixed number of subframes after a downlink subframe. This requirement ensures that a relay can send a hybrid automatic repeat request (HARQ) ACK/NACK report for received downlink packets. Therefore, even when it would be beneficial for uplink purposes to allocate more subframes to the relevant access link, the same settings for downlink may degrade downlink performance and the change may result in an overall performance deterioration.
Furthermore, it is often critical for a relay and its donor base station to have the same backhaul link configuration. Otherwise there is a risk that they will not be able to communicate with each other. As a result, signaling for such a reallocation of subframes may need to use a reliable signaling transport (e.g., Radio Resource Control (RRC) on top of Radio Link Control (RLC)/Media Access Control (MAC)). The reconfiguration of the relay and its donor base station may also need to be coordinated in time. Time synchronization can necessitate that further delays be added to the reconfiguration procedure to account for variations in the signaling delays (due to re-transmissions).
As a result, intelligently managing the allocation of transmission resources between a relay's access link and backhaul link can be critical to the relays performance. Additionally, the ability to adjust the allocation quickly and without significant complexity would be highly beneficial. Timely reallocation between the two links could significantly increase the performance of a relay and provide additional benefits.